Update: NASA press release is here.
NASA announced today that a vacuum leak in the French-built seismometer is forcing a cancellation of InSight’s scheduled March 2016 launch.
In a statement, NASA said, “After thorough examination, NASA managers have decided to suspend the March 2016 launch of the Interior Exploration using Seismic Investigations Geodesy and Heat Transport (InSight) mission. The decision follows unsuccessful attempts to repair an air leak on a key component of the mission’s science payload. NASA will hold a media teleconference at 3:30 p.m. EST today, Dec. 22, to provide details on this decision.”
As reported earlier, the sensor unit for the Seismic Experiment for Interior Structure (SEIS) instrument (silver dome at lower left, above) has a vacuum leak. This allows Martian air to get into the instrument, degrading its sensitivity and preventing it from working as designed. Just last week, the InSight spacecraft was delivered to Vandenberg Air Force Base in California for the final round of tests before launch.
As to when InSight might be rescheduled for launch, the next Mars launch window doesn’t occur for 26 months, pushing any launch attempt to 2018.